Found another bug - level 315 Grow Lancer, when talking to Marlon I get no quest offering, just '1) Conversation is over' as a dialog. Also if I talk to Sebina the Priest her dialog window appears titled 'Bull Fighter' and does the same thing, asks 'Do you need anything?' and gives me the 'Conversation is over' option. The option to click also doesn't close the window, so you need to hit the X.
EDIT: Found a trigger for the error...
NOTE: Found that this occurs if you have side quests. I have Zyro and a Gens quest, once I gave them up the usual dialog came back. However the bug still exists where I have no quest, I can only select '1) I'll be back when I'm stronger' but I'm level 317...
Will update this post if I find more errors in this test phase.